Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$52.61	4.281%	$54.8622	$54.86	$54.85	$54.90
Purchase #2	$55.61	10.758%	$61.5925	$61.59	$61.60	$61.60
Purchase #3	$249.55	4.354%	$260.4154	$260.42	$260.40	$260.40
Purchase #4	$10.39	8.830%	$11.3074	$11.31	$11.30	$11.30
Purchase #5	$193.83	9.659%	$212.552	$212.55	$212.55	$212.60
Purchase #6	$190.67	12.574%	$214.6448	$214.64	$214.65	$214.60
Purchase #7	$127.73	9.467%	$139.8222	$139.82	$139.80	$139.80
7 purchase totals =	$880.39		$955.1965	$955.19	$955.15	$955.20